Power amplification module

ABSTRACT

A power amplification module includes a first transistor which amplifies and outputs a radio frequency signal input to its base; a current source which outputs a control current; a second transistor connected to an output of the current source, a first current from the control current input to its collector, a control voltage generation circuit connected to the output and which generates a control voltage according to a second current from the control current; a first FET, the drain being supplied with a supply voltage, the source being connected to the base of the first transistor, and the gate being supplied with the control voltage; and a second FET, the drain being supplied with the supply voltage, the source being connected to the base of the second transistor, and the gate being supplied with the control voltage.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a power amplification module.

2. Background Art

In a mobile communication device, such as a mobile phone, a poweramplification module (power amplifier module) is used in order toamplify the power of a radio frequency (RF) signal to be transmitted toa base station. This power amplification module includes a poweramplifier which amplifies the RF signal, and a bias circuit whichsupplies a bias current to a transistor constituting the poweramplifier.

FIG. 10 is a diagram showing a configuration example of a poweramplification module using an emitter follower type (common collector)bias circuit (for example, Patent Document 1). A bias circuit 1000supplies a bias current to a bipolar transistor T100 constituting apower amplifier 1010, and has an emitter follower configuration. Abattery voltage V_(BAT) is applied to the collector of a bipolartransistor T110 constituting a bias circuit 1000.

In this configuration, if the bipolar transistors T100 and T110 are, forexample, heterojunction bipolar transistors (HBT), the base-emittervoltage V_(BE) of each bipolar transistor is about 1.3 V, and thus, thebattery voltage V_(BAT) of about 2.8 V is required in order to drive thebipolar transistor T110. For this reason, in general, the minimumvoltage of the battery voltage V_(BAT) is, for example, about 2.9 V.

On the other hand, in recent years, in a mobile communication device,such as a mobile phone, there has been demand for decreasing the minimumvoltage of the battery voltage V_(BAT) to about 2.5 V in order toimprove a talking time or a communication time. However, in theconfiguration using the emitter follower (common collector) type biascircuit 1000 described above, the battery voltage V_(BAT) of about 2.8 Vis required, and thus, it is not possible to cope with this requirement.

Accordingly, as a configuration capable of operating a bias circuit witha lower battery voltage V_(BAT), a configuration in which a FET is usedin a bias circuit has been suggested. FIG. 11 is a diagram showing aconfiguration example of a power amplification module using a FET in abias circuit (for example, Patent Document 2). As shown in FIG. 11, aFET (F100) is used in a bias circuit 1100 which supplies a bias currentto a bipolar transistor T100 of a power amplifier 1010.

However, as disclosed in Patent Document 2, a FET is used in the biascircuit, thereby making the battery voltage V_(BAT) for operating thebias circuit a low voltage. However, in the configuration disclosed inPatent Document 2, resistors R100 and R110 which output a controlvoltage to be applied to the gate of the FET (F100) are different intemperature characteristics from the bipolar transistor T100. For thisreason, in the configuration disclosed in Patent Document 2, the gain ofthe power amplifier 1010 fluctuates with change in temperature.

CITATION LIST Patent Documents

[Patent Document 1] JP11-330866 A

[Patent Document 2] JP2010-233171 A

SUMMARY OF THE INVENTION

The invention has been accomplished in consideration of this situation,and an object of the invention is to provide a power amplificationmodule capable of achieving low-voltage driving and improvingtemperature characteristics.

A power amplification module according to an aspect of the inventionincludes a first bipolar transistor which amplifies and outputs a radiofrequency signal input to the base of the first bipolar transistor, acurrent source which outputs a control current, a second bipolartransistor which is connected to an output terminal of the currentsource, a first current out of the control current being input to thecollector of the second bipolar transistor, a control voltage generationcircuit which is connected to the output terminal of the current sourceand generates a control voltage according to a second current out of thecontrol current, a first FET, the drain of the first FET being suppliedwith a power supply voltage, the source of the first FET being connectedto the base of the first bipolar transistor, and the gate of the firstFET being supplied with the control voltage, and a second FET, the drainof the second FET being supplied with the power supply voltage, thesource of the second FET being connected to the base of the secondbipolar transistor, and the gate of the second FET being supplied withthe control voltage.

According to the invention, it is possible to provide a poweramplification module capable of achieving low-voltage driving andimproving temperature characteristics.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a configuration example of a transmissionunit including a power amplification module according to an embodimentof the invention.

FIG. 2 is a block diagram showing the configuration of a poweramplification module.

FIG. 3 is a diagram showing an example of the configurations of a poweramplifier and a bias circuit.

FIG. 4 is a simulation result showing an example of fluctuation in biascurrent I_(BIAS) due to variation in threshold voltage V_(TH) of FETs ina bias circuit.

FIG. 5 is a configuration example for increasing a one-round loop gainin the bias circuit.

FIG. 6 is a simulation result showing an example of fluctuation in biascurrent I_(BIAS) due to variation in threshold voltage V_(TH) of FETs ina bias circuit.

FIG. 7 is a simulation result showing an example of fluctuation in biascurrent I_(BIAS) according to variation in pair property of thresholdvoltages of FETs in the bias circuit.

FIG. 8 is a diagram showing an example of the configuration of the biascircuit for suppressing an influence of variation in pair property ofthreshold voltages of FETs.

FIG. 9 is a simulation result showing an example of fluctuation in biascurrent I_(BIAS) due to variation in threshold voltage V_(TH1) of a FETin a bias circuit.

FIG. 10 is a diagram showing a configuration example of a poweramplification module using an emitter follower (common collector) typebias circuit.

FIG. 11 is a diagram showing a configuration example of a poweramplification module using a FET in a bias circuit.

FIG. 12 is a diagram showing an example of the configuration of thepower amplification module for suppressing a leak current.

FIG. 13 is a diagram showing the configuration of an example biascircuit.

FIG. 14 is a diagram showing the configuration of an example biascircuit.

FIG. 15 is a diagram showing the configuration of an example biascircuit.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the invention will be described referring tothe drawings. FIG. 1 is a diagram showing the configuration example of atransmission unit 100 including a power amplification module 130. Thetransmission unit 100 is, for example used to transmit various signals,such as sound or data, to a base station from a mobile communicationdevice, such as a mobile phone. Although the mobile communication deviceincludes a reception unit which receives signals from the base station,description of the reception unit will be omitted.

As shown in FIG. 1, the transmission unit 100 includes a modulationsection 110, a transmission power control section 120, a poweramplification module 130, a front-end section 140, and an antenna 150.

The modulation section 110 modulates an input signal based on amodulation system, such as high speed uplink packet access (HSUPA) orlong term evolution (LTE), and generates an RF signal for radiotransmission. The frequency of the RF signal is, for example, abouthundreds of MHz to several GHz.

The transmission power control section 120 adjusts the power of the RFsignal based on a transmission power control signal and outputs the RFsignal. The transmission power control signal is generated based on, forexample, an adaptive power control (APC) signal transmitted from thebase station. For example, the base station measures a signal from themobile communication device, thereby transmitting the APC signal to themobile communication device as a command to adjust transmission power inthe mobile communication device to an appropriate level.

The power amplification module 130 amplifies the power of the RF signal(RF_(IN)) output from the transmission power control section 120 to alevel necessary for transmission to the base station and outputs anamplified signal (RF_(OUT)).

The front-end section 140 performs filtering on the amplified signal,switching between the amplified signal and the reception signal receivedfrom the base station, or the like. The amplified signal output from thefront-end section 140 is transmitted to the base station through theantenna 150.

FIG. 2 is a block diagram showing the configuration of a poweramplification module 130A which is an example of the power amplificationmodule 130. As shown in FIG. 2, the power amplification module 130Aincludes power amplifiers 200A and 200B, bias circuits 210A and 210B, abias control circuit 220, matching circuits (MN: Matching Networks)230A, 230B, and 230C, and inductors L1 and L2.

The power amplifiers 200A and 200B amplify the input RF signal andoutput the amplified signal. In the power amplification module 130A, thepower amplifier 200A becomes an initial-stage (drive-stage) amplifier,and the power amplifier 200B becomes a back-stage (power-stage)amplifier. In the configuration shown in FIG. 2, although the poweramplifiers are provided in a two-stage configuration, a power amplifiermay be provided in a single-stage configuration or power amplifiers maybe provided in a three or more-stage configuration.

The bias circuits 210A and 210B supply a bias current to the poweramplifiers 200A and 200B based on a bias control voltage V_(BIAS)supplied from the bias control circuit 220.

The bias control circuit 220 outputs the bias control voltage V_(BIAS)for controlling the bias current to the bias circuits 210A and 210B. Thebias control circuit 220 can adjust the output level of the bias controlvoltage V_(BIAS) in order to vary the gains of the power amplifiers 200Aand 200B.

The matching circuits 230A, 230B, and 230C are provided for impedancematching between the front and back circuits, and can be configuredusing, for example, a capacitor or an inductor.

FIG. 3 is a diagram showing examples of the configurations of the poweramplifier 200A and the bias circuit 210A. The configurations of thepower amplifier 200B and the bias circuit 210B shown in FIG. 2 are thesame as the configurations of the power amplifier 200A and the biascircuit 210A, and thus description thereof will be omitted.

As shown in FIG. 3, the power amplifier 200A includes a bipolartransistor T1. The bipolar transistor T1 is, for example, a HBT. In thebipolar transistor T1, a power supply voltage V_(CC) is applied to thecollector through an inductor L1, the emitter is grounded, and an RFsignal (RF_(IN1)) is input to the base through the matching circuit230A. The base of the bipolar transistor T1 is also supplied with a biascurrent I_(BIAS) from the bias circuit 210A. An amplified signal(RF_(OUT1)) of the RF signal (RF_(IN1)) is output from the collector ofthe bipolar transistor T1.

A bias circuit 210A-1 which is an example of the bias circuit 210Aincludes a current source 300, a bipolar transistor T2, resistors R1 andR2, FETs (F1, F2), and a capacitor C1.

The current source 300 generates a control current I_(CTRL) according tothe bias control voltage V_(BIAS) using the battery voltage V_(BAT) as apower supply voltage.

In the bipolar transistor T2, the collector is connected to an outputterminal of the current source 300, and the emitter is grounded. Acurrent I₁ which is a part of the control current I_(CTRL) output fromthe current source 300 is input to the collector of the bipolartransistor T2. Similarly to the bipolar transistor T1, the bipolartransistor T2 is, for example, a HBT. The bipolar transistor T2 can havea size smaller than the bipolar transistor T1. The size of the bipolartransistor refers to an area occupied by the number of fingers of thetransistor.

The resistor R1 and the resistor R2 connected in series are connected tothe output terminal of the current source 300. A current I₂, which is apart of the control current I_(CTRL) output from the current source 300,is input to the resistor R1 and the resistor R2. The resistors R1 and R2constitute a control voltage generation circuit which generates acontrol voltage V_(CTRL) according to the current I₂.

In the FET F1, the drain is supplied with the battery voltage V_(BAT) asa power supply voltage, the source is connected to the base of thebipolar transistor T1, and the gate is supplied with the control voltageV_(CTRL). In the FET F2, the drain is supplied with the battery voltageV_(BAT) as a power supply voltage, the source is connected to the baseof the bipolar transistor T2, and the gate is supplied with the controlvoltage V_(CTRL). The FETs (F1, F2) can be depletion type FETs. The FETF2 can have a size smaller than the FET F1. The size of the FET refersto an occupancy area of a gate width and a gate length.

In the capacitor C1, one end is connected to the output terminal of thecurrent source 300, and the other end is grounded.

In the bias circuit 210A-1 having this configuration, the bias currentI_(BIAS) is supplied from the source of the FET F1 to the base of thebipolar transistor T1. Hereinafter, the operation of the bias circuit210A-1 will be described.

The FETs (F1, F2) and the bipolar transistor T2 operate with the controlcurrent I_(CTRL) from the current source 300. If the potential of pointQ (the base potential of the bipolar transistor T2) shown in FIG. 3rises with the operation of the FET F2, the current I₁ flowing in thebipolar transistor T2 increases. If the current I₁ increases, thecurrent I₂ flowing in the resistors R1 and R2 decreases. If the currentI₂ decreases, the control voltage V_(CTRL) falls. If the control voltageV_(CTRL) falls, a current I₃ flowing in the FET F2 decreases, and thecurrent I₁ flowing in the bipolar transistor T2 decreases. If thecurrent I₁ decreases, the current I₂ flowing in the resistors R1 and R2increases. If the current I₂ increases, the control voltage V_(CTRL)rises. If the control voltage V_(CTRL) rises, the current I₃ flowing inthe FET F2 increases, and the current I₁ flowing in the bipolartransistor T2 increases.

In this way, in the bias circuit 210A-1, a closed loop operation isperformed, and the control voltage V_(CTRL) settles at a certain point.The bias current I_(BIAS) according to the control voltage V_(CTRL) isoutput from the source of the FET F1. Accordingly, the bias currentI_(BIAS) becomes a current according to the bias control voltageV_(BIAS).

In this closed loop, the control voltage V_(CTRL) supplied to the gateof the FET F1 changes according to the temperature characteristics ofthe bipolar transistor T2 and the FET F2. Accordingly, the bias currentI_(BIAS) supplied to the bipolar transistor T1 changes according to thetemperature characteristics of the bipolar transistor T2 and the FET F2.The temperature characteristics of the bipolar transistor T1 are thesame as the temperature characteristics of the bipolar transistor T2.The temperature characteristics of the FET F1 are the same as thetemperature characteristics of the FET F2. Accordingly, change in thebias current I_(BIAS) according to the temperature characteristics ofthe bipolar transistor T2 and the FET F2 is also made according to thetemperature characteristics of the bipolar transistor T1 and the FET F1.With this, it is possible to suppress fluctuation in gain of the poweramplification module 130 due to change in temperature.

In the bias circuit 210A-1, since the FET F1 is used as a transistorconnected to the base of the bipolar transistor T1, even if the batteryvoltage V_(BAT) is about 2.5 V, the bias circuit 210A-1 is operable.When the FET F1 is a depletion type FET, even if the battery voltageV_(BAT) is about 2.0 V, it is possible to operate the bias circuit210A-1.

In FIG. 3, although the power amplifier 200A and the bias circuit 210Ahave been described, the same applies to the power amplifier 200B andthe bias circuit 210B. Accordingly, the power amplification module 130Acan be driven with the battery voltage V_(BAT) which is a low voltage ofabout 2.5 V (or about 2.0 V), and can have improved temperaturecharacteristics.

On the other hand, there is variation in threshold voltage V_(TH) of theFETs (F1, F2) used in the bias circuit 210A-1 shown in FIG. 3. It isconsidered that this variation causes fluctuation in bias currentI_(BIAS) output from the FET F1 to the base of the bipolar transistorT1, and also causes fluctuation in gain of the power amplificationmodule 130A.

FIG. 4 is a simulation result showing an example of fluctuation in biascurrent I_(BIAS) due to variation in threshold voltage V_(TH) of theFETs (F1, F2) in the bias circuit 210A-1 shown in FIG. 3. In FIG. 4, thehorizontal axis represents the control current I_(CTRL) (A) which isoutput from the current source 300, and the vertical axis represents thebias current I_(BIAS) (mA). In the example shown in FIG. 4, when thethreshold voltage V_(TH) is increased or decreased from the reference by0.1 V, fluctuation of about 10 mA occurs in the bias current I_(BIAS).

In order to reduce the influence of variation in threshold voltageV_(TH) of the FETs (F1, F2), increasing the one-round loop gain G in theabove-described closed loop when viewed from the Q point in the biascircuit 210A-1 may be considered.

If the gain of the bipolar transistor T2 is Q, the emitter resistance ofthe bipolar transistor T2 is R_(e), and the resistance values of theresistors R1 and R2 are respectively R1 and R2, a one-round loop gain Gin the bias circuit 210A-1 shown in FIG. 3 isG=(Q/R_(e))×(R1+R2)×{R2/(R1+R2)}=(Q/R_(e))×R2. Accordingly, if theresistance value of the resistor R2 is set to a large value, theone-round loop gain G can be increased. However, setting the resistancevalue of the resistor R2 to a large value leads to an increase in chipsize.

FIG. 5 is a configuration example for increasing the one-round loop gainG in the bias circuit 210A. A bias circuit 210A-2 shown in FIG. 5includes a bipolar transistor T3 instead of the resistor R1 in the biascircuit 210A-1 shown in FIG. 3. Other configurations are the same asthose shown in FIG. 3, and thus, description thereof will not berepeated. In the bipolar transistor T3, the collector is supplied withthe battery voltage V_(BAT), the emitter is connected to one end of theresistor R2, and the base is connected to the output terminal of thecurrent source 300.

In the bias circuit 210A-2 shown in FIG. 5, the current I₂ which is apart of the control current I_(CTRL) from the current source 300 isinput to the base of the bipolar transistor T3. A current I₄, obtainedby amplifying the current I₂, is output from the emitter of the bipolartransistor T3, and the current I₄ is converted to the control voltageV_(CTRL) by the resistor R2. That is, the bipolar transistor T3 and theresistor R2 constitute a control voltage generation circuit whichgenerates the control voltage V_(CTRL) according to the current I₂.

If the current amplification factor of the bipolar transistor T3 ishFE_(T3), the one-round loop gain G in the bias circuit 210A-2 shown inFIG. 5 is G=(Q/re)×R2×hFE_(T3). The current amplification factorhFE_(T3) of the bipolar transistor T3 is, for example, a magnitude ofabout 100. Accordingly, in the bias circuit 210A-2 shown in FIG. 5, itis possible to increase the one-round loop gain G by the currentamplification factor of the bipolar transistor T3 without setting theresistance value of the resistor R2 to a large value. With this, it ispossible to suppress fluctuation in gain of the power amplificationmodule 130A due to variation in threshold voltage V_(TH) of the FETs(F1, F2).

FIG. 6 is a simulation result showing an example of fluctuation in biascurrent I_(BIAS) due to variation in threshold voltage V_(TH) of theFETs (F1, F2) in the bias circuit 210A-2 shown in FIG. 5. In FIG. 6, thehorizontal axis represents the control current I_(CTRL) (A) which isoutput from the current source 300, and the vertical axis represents thebias current I_(BIAS) (mA). In the example shown in FIG. 6, when thethreshold voltage V_(TH) is increased or decreased from the reference by0.1 V, the fluctuation width of the bias current I_(BIAS) is less than 1mA. In this way, it is understood from the simulation result that theuse of the configuration shown in FIG. 5 can allow suppression offluctuation in bias current I_(BIAS) due to variation in thresholdvoltage V_(TH) of the FETs (F1, F2).

On the other hand, in the bias circuit 210A-2 shown in FIG. 5, variationin pair property may occur in the threshold voltage of the FETs (F1,F2). Variation in pair property of the threshold voltages of the FETs(F1, F2) is the difference between the threshold voltage V_(TH1) of theFET F1 and the threshold voltage V_(TH2) of the FET F2 in the samemodule. FIG. 7 is a simulation result showing an example of fluctuationin bias current I_(BIAS) according to variation in pair property of thethreshold voltages of the FETs (F1, F2) in the bias circuit 210A-2 shownin FIG. 5. In FIG. 7, the horizontal axis represents the control currentI_(CTRL) (A) which is output from the current source 300, and thevertical axis represents the bias current I_(BIAS) (mA). In the exampleshown in FIG. 7, fluctuation of about 10 to 20 mA occurs in the biascurrent I_(BIAS) due to variation (±10 mV) in pair property of thethreshold voltages of the FETs (F1, F2).

FIG. 8 is a diagram showing an example of the configuration of the biascircuit 210A for suppressing the influence of variation in pair propertyof the threshold voltages of the FETs (F1, F2). A bias circuit 210A-3shown in FIG. 8 includes a resistor R3 instead of the FET F2 shown inFIG. 5. Other configurations are the same as those shown in FIG. 5, andthus, description will not be repeated. In the bias circuit 210A-3 shownin FIG. 8, the source of the FET F1 is connected to the base of thebipolar transistor T1 and is connected to one end of the resistor R3.The other end of the resistor R3 is connected to the base of the bipolartransistor T2. That is, in the bias circuit 210A-3 shown in FIG. 8, theFET F1 is used to generate the control voltage V_(CTRL) by the closedloop and to supply the bias current I_(BIAS) to the bipolar transistorT1. In the bias circuit 210-3 shown in FIG. 8, since only one FET isused, variation in pair property does not occur.

FIG. 9 is a simulation result showing an example of fluctuation in biascurrent I_(BIAS) due to variation in threshold voltage V_(TH1) of theFET F1 in the bias circuit 210A-3 shown in FIG. 8. In FIG. 9, thehorizontal axis represents the control current I_(CTRL) (A) which isoutput from the current source 300, and the vertical axis represents thebias current I_(BIAS) (mA). In the example shown in FIG. 9, when thethreshold voltage V_(TH1) is increased or decreased from the referenceby 0.1 V, the fluctuation width of the bias current I_(BIAS) is lessthan 1 mA. In this way, it is understood that the use of theconfiguration shown in FIG. 8 can allow suppression of fluctuation inbias current I_(BIAS) due to variation in threshold voltage V_(TH1) ofthe FET F1.

That is, in the bias circuit 210A-3 shown in FIG. 8, variation in pairproperty of the threshold voltages of the FETs (F1, F2) does not occur,and it is possible to suppress fluctuation in bias current I_(BIAS) dueto variation in threshold voltage V_(TH1) of the FET F1. Accordingly, itis possible to suppress fluctuation in gain of the power amplificationmodule 130A.

On the other hand, in the bias circuit 210A, for example, if adifference is generated between the base-emitter voltages of the bipolartransistors T1 and T2 or the threshold voltages of the FETs (F1, F2) dueto manufacturing variation (variation in pair property), even when thecontrol current I_(CTRL) is substantially zero, a leak current may flowin the bipolar transistor T1.

FIG. 12 is a diagram showing an example of the configuration of thepower amplification module 130 for suppressing a leak current. A poweramplification module 130B shown in FIG. 12 includes bias circuits 210A′and 210B′ instead of the bias circuits 210A and 210B in the poweramplification module 130A shown in FIG. 2. The power amplificationmodule 130B also includes a power supply control circuit 1300. In thepower amplification module 130B, other configurations are the same asthose of the power amplification module 130A, and thus, theseconfigurations are represented by the same reference numerals anddescription thereof will not be repeated.

The bias circuits 210N and 210B′ are the same as the bias circuits 210Aand 210B of the power amplification module 130A, except that aregulation voltage V_(REG) is supplied as a power supply voltage. Thedetails will be described below.

The power supply control circuit 1300 outputs the regulation voltageV_(REG) based on the battery voltage V_(BAT) and an amplificationcontrol signal CTRL_(AMP). The amplification control signal CTRL_(AMP)is a signal which indicates whether or not to perform the amplificationof the RF signal in the power amplifiers 200A and 200B.

When the amplification control signal CTRL_(AMP) indicates performingthe amplification of the RF signal in the power amplifiers 200A and200B, the power supply control circuit 1300 outputs the battery voltageV_(BAT) as the regulation voltage V_(REG).

When the amplification control signal CTRL_(AMP) indicates notperforming the amplification of the RF signal in the power amplifiers200A and 200B, the power supply control circuit 1300 reduces theregulation voltage V_(REG). Specifically, for example, the power supplycontrol circuit 1300 sets the regulation voltage V_(REG) to a zerolevel. In this case, the power supply control circuit 1300 may reducethe regulation voltage V_(REG) to a level (for example, less than 2.0V), at which the bipolar transistor T1 does not operate, instead of thezero level.

FIG. 13 is a diagram showing the configuration of a bias circuit 210A′-1which is an example of the bias circuit 210A′. The configuration of thebias circuit 210B′ is the same as that of the bias circuit 210A′, andthus, description thereof will not be repeated. The same configurationsas those in the bias circuit 210A-1 shown in FIG. 3 are represented bythe same reference numerals, and description thereof will not berepeated.

As shown in FIG. 13, in the bias circuit 210A′-1, the regulation voltageV_(REG) is supplied as a power supply voltage to the drains of the FETs(F1, F2). As described above, when the amplification of the RF signal isnot performed in the power amplifier 200A, the regulation voltageV_(REG) falls to, for example, the zero level. Accordingly, in thiscase, it is possible to suppress a leak current from flowing in thebipolar transistor T1.

Similarly, the bias circuits 210A-2 and 210A-3 shown in FIGS. 5 and 8can be changed to a configuration in which the regulation voltageV_(REG) is supplied as a power supply voltage. Specifically, as anexample of the bias circuit 210A′, the configurations of bias circuits210A′-2 and 210A′-3 shown in FIGS. 14 and 15 can be used.

As above, these embodiments have been described. According to the poweramplification module 130 of this embodiment, the FET F1 can be used as atransistor for generating the bias current I_(BIAS), whereby the batteryvoltage V_(BAT) can be operable even at about 2.5 V. The control voltageV_(CTRL) which is supplied to the gate of the FET F1 is controlled usingthe bipolar transistor T2 having the same temperature characteristics asthe bipolar transistor T1 and the FET F2 having the same temperaturecharacteristics as the FET F1, whereby it is possible to suppressfluctuation in gain of the power amplification module 130 due to changein temperature.

According to these embodiments, as shown in FIG. 5, the bipolartransistor T3 can be used as a circuit for generating the controlvoltage V_(CTRL), whereby it is possible to increase the gain of theclosed loop which generates the control voltage V_(CTRL) and to reducethe influence of variation in threshold voltage of the FET. With this,it is possible to suppress fluctuation in gain of the poweramplification module 130.

According to these embodiments, in the configuration shown in FIG. 3 or5, the sizes of the bipolar transistor T2 and the FET F2 for generatingthe control voltage V_(CTRL) can be made smaller than the sizes of thebipolar transistor T1 and the FET F1. With this, it is possible toreduce current consumption in a circuit which generates the controlvoltage V_(CTRL).

According to these embodiments, the FETs (F1, F2) can be depletion typeFETs, whereby it is possible to operate the power amplification module130 even if the battery voltage V_(BAT) is about 2.0 V.

According to these embodiments, as shown in FIG. 8, one FET F1 can beused to generate the control voltage V_(CTRL) and to supply the biascurrent I_(BIAS), whereby it is possible to suppress fluctuation in gainof the power amplification module 130 due to variation in pair property.

According to these embodiments, as shown in FIGS. 12 to 15, when theamplification of the RF signal is not performed in the power amplifiers200A and 200B, the power supply voltage which is supplied to the FETsconstituting the bias circuits 210A′ and 210B′ falls, whereby it ispossible to suppress a leak current from flowing in the bipolartransistor T1.

The respective embodiments described above facilitate understanding ofthe invention and are not to be interpreted as limiting the invention.The invention may be altered and improved without departing from thegist of the invention, and equivalents are intended to be embracedtherein. That is, those skilled in the art can appropriately modify theembodiments, and these modifications are also encompassed within thescope of the invention as long as the modifications include the featuresof the invention. For example, the components included in theembodiments and the arrangements, the materials, the conditions, theshapes, the sizes, and the like of the components are not limited to theillustrated ones and can be varied appropriately. The componentsincluded in the embodiments can be combined as long as the combinationis technically possible, and the combined components are alsoencompassed within the scope of the invention as long as the combinedcomponents include the features of the invention.

DESCRIPTION OF REFERENCE NUMERALS

100 transmission unit

110 modulation section

120 transmission power control section

130 power amplification module

140 front-end section

150 antenna

200 power amplifier

210 bias circuit

220 bias control circuit

230 matching circuit

300 current source

T1 to T3 bipolar transistor

F1 to F2 FET

R1 to R3 resistor

C1 capacitor

What is claimed is:
 1. A power amplification module comprising: a firstbipolar transistor which amplifies and outputs a radio frequency signalinput to the base of the first bipolar transistor; a current sourcewhich outputs a control current; a second bipolar transistor which isconnected to an output terminal of the current source, a first currentout of the control current being input to the collector of the secondbipolar transistor; a control voltage generation circuit which isconnected to the output terminal of the current source and generates acontrol voltage according to a second current out of the controlcurrent; a first FET, the drain of the first FET being supplied with apower supply voltage, the source of the first FET being connected to thebase of the first bipolar transistor, and the gate of the first FETbeing supplied with the control voltage; and a second FET, the drain ofthe second FET being supplied with the power supply voltage, the sourceof the second FET being connected to the base of the second bipolartransistor, and the gate of the second FET being supplied with thecontrol voltage.
 2. The power amplification module according to claim 1,wherein the control voltage generation circuit includes a firstresistor, a first end of is the first resistor being connected to theoutput terminal of the current source, and a second resistor, a firstend of is the second resistor being connected to a second end of thefirst resistor and a second end of is the second resistor grounded, andthe control voltage is output from a connection point of the first andsecond resistors.
 3. The power amplification module according to claim1, wherein the control voltage generation circuit includes a thirdbipolar transistor, the collector of the third bipolar transistor beingsupplied with the power supply voltage and the base of the third bipolartransistor being connected to the output terminal of the current source,and a second resistor, a first end of the second resistor beingconnected to the emitter of the third bipolar transistor and a secondend of is the second resistor being grounded, and the control voltage isoutput from a connection point of the third bipolar transistor and thesecond resistor.
 4. The power amplification module according to claim 1,wherein a size of the second bipolar transistor is smaller than a sizeof the first bipolar transistor, and a size of the second FET is smallerthan a size of the first FET.
 5. The power amplification moduleaccording to claim 1, wherein the first and second FETs are depletiontype FETs.
 6. The power amplification module according to claim 1,further comprising: a power supply control circuit which, based on anamplification control signal instructing whether or not to perform theamplification of the radio frequency signal in the first bipolartransistor, reduces the power supply voltage when the amplification isnot performed.
 7. The power amplification module according to claim 2,wherein a size of the second bipolar transistor is smaller than a sizeof the first bipolar transistor, and a size of the second FET is smallerthan a size of the first FET.
 8. The power amplification moduleaccording to claim 3, wherein a size of the second bipolar transistor issmaller than a size of the first bipolar transistor, and a size of thesecond FET is smaller than a size of the first FET.
 9. The poweramplification module according to claim 2, wherein the first and secondFETs are depletion type FETs.
 10. The power amplification moduleaccording to claim 3, wherein the first and second FETs are depletiontype FETs.
 11. The power amplification module according to claim 4,wherein the first and second FETs are depletion type FETs.
 12. The poweramplification module according to claim 2, further comprising: a powersupply control circuit which, based on an amplification control signalinstructing whether or not to perform the amplification of the radiofrequency signal in the first bipolar transistor, reduces the powersupply voltage when the amplification is not performed.
 13. The poweramplification module according to claim 3, further comprising: a powersupply control circuit which, based on an amplification control signalinstructing whether or not to perform the amplification of the radiofrequency signal in the first bipolar transistor, reduces the powersupply voltage when the amplification is not performed.
 14. The poweramplification module according to claim 4, further comprising: a powersupply control circuit which, based on an amplification control signalinstructing whether or not to perform the amplification of the radiofrequency signal in the first bipolar transistor, reduces the powersupply voltage when the amplification is not performed.
 15. The poweramplification module according to claim 5, further comprising: a powersupply control circuit which, based on an amplification control signalinstructing whether or not to perform the amplification of the radiofrequency signal in the first bipolar transistor, reduces the powersupply voltage when the amplification is not performed.
 16. The poweramplification module according to claim 7, further comprising: a powersupply control circuit which, based on an amplification control signalinstructing whether or not to perform the amplification of the radiofrequency signal in the first bipolar transistor, reduces the powersupply voltage when the amplification is not performed.
 17. The poweramplification module according to claim 8, further comprising: a powersupply control circuit which, based on an amplification control signalinstructing whether or not to perform the amplification of the radiofrequency signal in the first bipolar transistor, reduces the powersupply voltage when the amplification is not performed.
 18. The poweramplification module according to claim 9, further comprising: a powersupply control circuit which, based on an amplification control signalinstructing whether or not to perform the amplification of the radiofrequency signal in the first bipolar transistor, reduces the powersupply voltage when the amplification is not performed.
 19. The poweramplification module according to claim 10, further comprising: a powersupply control circuit which, based on an amplification control signalinstructing whether or not to perform the amplification of the radiofrequency signal in the first bipolar transistor, reduces the powersupply voltage when the amplification is not performed.
 20. The poweramplification module according to claim 11, further comprising: a powersupply control circuit which, based on an amplification control signalinstructing whether or not to perform the amplification of the radiofrequency signal in the first bipolar transistor, reduces the powersupply voltage when the amplification is not performed.